The invention relates generally to semiconductor devices and, more particularly, to silicon carbide-based devices that utilize a junction termination extension.
Breakdown voltage of the reverse-blocking junction typically serves to limit the maximum reverse voltage that a semiconductor device formed with a p-n junction can withstand. Such a blocking junction may comprise, for example, a p-n junction of a thyristor, a diode, a bipolar transistor, an insulated-gate transistor, or a corresponding junction in a metal-oxide-semiconductor field-effect transistor (MOSFET). Avalanche breakdown occurs in such a device at a voltage substantially less than the ideal breakdown voltage because excessively high electric fields are present at certain locations (“high field points”) in the device under reverse bias. A high field point of a blocking junction under reverse bias usually occurs slightly above the metallurgical junction along a region of curvature, such as that at the end of the junction.
In particular, breakdown voltage is critical for high power devices, such as silicon carbide (SiC) devices, and related properties, such as robustness to active dose and interface charge variation, are more significant in SiC devices, than in silicon (Si) based devices.
Semiconductor devices may utilize any of various structures and methods to achieve an increase in the breakdown voltage of a p-n junction, for example close to p-n junction entitlement. For example, junction termination extension (JTE) regions may be utilized near terminated portions of the p-n junction. In general, a JTE region may be considered as a more lightly doped extension of a heavily doped semiconductor region that adjoins a semiconductor region of the opposite conductivity type and which is usually lightly doped, to form the foregoing p-n junction. The principal function of the JTE region is to reduce the high concentration of electric fields that would otherwise exist in the vicinity of the non-terminated portion of the p-n junction, and especially at the high field points (which are typically near the corners of the locally doped regions), by laterally extending the blocking junction.
In addition to breakdown voltage, the design of the JTE affects a number of critical properties of the semiconductor device, including reliability, fabrication process complexity, and charge tolerance, and many of the affected properties have complex interrelationships.
It would therefor be desirable to provide a JTE design that improves the critical properties of silicon-carbide based semiconductor devices, such as break down voltage, charge tolerance and reliability.